The interaction between several different metal ions and H2O along with CO2 has been researched theoretically in the CO2 photocatalytic reduction with H2O system at the B3LYP level by DFT.The computational results rev...The interaction between several different metal ions and H2O along with CO2 has been researched theoretically in the CO2 photocatalytic reduction with H2O system at the B3LYP level by DFT.The computational results revealed that relatively high valence metal ions loaded on TiO2 activated the H2O and CO2 consumingly,and it might be looked as some proofs for modified photocatalyst selecting.In addition,the metal ions conducted photoelectrons to prevent the re-combination of photoelectrons and holes during the reaction process.展开更多
Recently, Hsieh and Horng [1] published the paper entitled as above. In section 3 results and discussion, the authors mentioned the first and the second order kinetic models without any quotations. In fact these two k...Recently, Hsieh and Horng [1] published the paper entitled as above. In section 3 results and discussion, the authors mentioned the first and the second order kinetic models without any quotations. In fact these two kinetic models have been published [2-5]. In order to distinguish a kinetics model based on the ad- sorption capacity of a solid from the one based on the concentration of a solution, Lagergren＇s first-order rate equation has been called pseudo-first-order [6-7]. The Lagergren＇s equation has been widely cited, but there are far more mistakes made in the quotation and in the reference section of papers, including the title, the author＇s name, journal title, year of publishing, volume, and page number [3]. In addition, the second order kinetic expression for the adsorption systems of divalent metal ions using sphagnum moss peat has been reported by Ho [8].展开更多
The microhydration structure of nickel sulfate aqueous solution has been determined via density functional theory (DFT) calculation and extended X-ray absorption fine structure (EXAFS) spectroscopy.The geometric optim...The microhydration structure of nickel sulfate aqueous solution has been determined via density functional theory (DFT) calculation and extended X-ray absorption fine structure (EXAFS) spectroscopy.The geometric optimization and energy calculation of nickel sulfate hydrated clusters of the molecular formula [NiSO4(H2O)n ]^0 (n=1-12) were determined via DFT using the B3LYP method.Several possible initial structures were considered for clusters of each size to locate the equilibrium geometry.Based on the DFT calculation,the favorable structure of Ni^2+ includes the six-coordinated form of [NiSO4(H2O)n ]^0 clusters.The results of hydration energy calculation suggest that the six-coordinated contact ion pair (CIP) is the stable configuration for small hydration clusters (n≤5),while the solvent-shared ion pair (SSIP) represents the favorable structure for medium hydration clusters (6≤n≤10).The solvent is separated by x water molecules (xSIP,x≥2 is the number of water molecule between Ni^2+ and SO4^2-) in larger hydration clusters (n≥11).The EXAFS analysis of the NiSO 4 aqueous solutions and NiSO4 ·6H2O solid established that Ni^2+ was surrounded by six water molecules tightly forming an octahedral structure in the first hydration shell,and no CIP was found from 0.70 mol/L to 2.22 mol/L (near saturation).The Ni-O distance and coordinated number were 2.040±0.020 and 6.0±1.0,respectively.These results are consistent with the DFT calculations for [NiSO4(H2O)n ]^0 clusters.DFT and EXAFS are powerful techniques that can be used to enhance the resolution of NiSO 4 solution microstructure.展开更多
The utilization of Ca ion as assistant depressant of CMC on talc has been widely reported.Thus,the study on the adsorption mechanism of Ca ion on talc surface is very crucial for understanding the performance of CMC o...The utilization of Ca ion as assistant depressant of CMC on talc has been widely reported.Thus,the study on the adsorption mechanism of Ca ion on talc surface is very crucial for understanding the performance of CMC on talc depression.In this paper,mechanism insights into hydrated Ca ion adsorption on talc(001) basal surface were creatively provided using DFT calculation.[Ca(H_(2)O)_6]^(2+) and [Ca(OH)(H_(2)O)_(3)]^(+) were determined as the effective hydrate components for Ca ion adsorption,and the top O site was the most favorable position for their adsorptions on talc surface.Furthermore,the adsorption mechanisms of [Ca(H_(2)O)_6]^(2+) and [Ca(OH)(H_(2)O)_(3)]^(+) on talc surface were found to be not the Ca-O chemical bond,but the hydrogen bonding formed by the H atom of the H_(2)O ligand and the surface O atom.H_(2)O acted like a bridge to connect them to the talc surface.Moreover,the hydrogen bonding was formed due to the hybridization of H 1s orbital with the O 2s,O 2p orbitals.Simultaneously,electrons transferred between the H atom and the surface O atom.This work provides theoretical insights into the Ca ion adsorption on talc surface,which can help deeply understand the talc flotation using CMC as depression.展开更多
The rational design of strong affinity adsorbents for heavy metal ions removal remains a critical challenge for water treatment.In this study,amorphous molybdenum sulfide composites(EDTA-MoSx(x=2,3))were fabricated vi...The rational design of strong affinity adsorbents for heavy metal ions removal remains a critical challenge for water treatment.In this study,amorphous molybdenum sulfide composites(EDTA-MoSx(x=2,3))were fabricated via a facile hydrothermal method mediated by EDTA,which was applied to heavy metal ions(Cu^(2+),Cd^(2+),Pb^(2+),Zn^(2+)and Ni^(2+))removal from aqueous solutions.A case study for Cu^(2+)ions showed that the adsorption capacity of EDTA-MoSx(x=2,3)was superior to crystalline phase MoS2 at pH 6.0 with an initial concentration of 200 mg/L.Adsorption mechanisms of different sulfide groups and—COOH of EDTA-MoSx(x=2,3)were verified systematically via a series of experiments,characterizations,and density functional theory(DFT)calculations.Both bridging S_(2)^(2-)and—COOH covalently bonded with Cu^(2+)ions were ascribed to the critical factors for this enhanced removal efficiency on the surface of EDTA-MoSx(x=2,3).This work offers a new method to enhance the adsorption performance of molybdenum sulfide-based materials by controlling crystallinity mediated with an organic complex small molecule.展开更多
Ag-and Pt-doped WO3-0.33 H2O nanorods with high response and selectivity to NH3 were synthesized from a tungsten-containing mine ral of scheelite concentrate by a simple combined process,namely by a high pressure leac...Ag-and Pt-doped WO3-0.33 H2O nanorods with high response and selectivity to NH3 were synthesized from a tungsten-containing mine ral of scheelite concentrate by a simple combined process,namely by a high pressure leaching method to obtain tungstate ions-containing leaching solution and followed by a hydrothermal method to prepare corresponding nanorods.The microstructure and NH3 sensing perfo rmance of the final products were investigated systematically.The microstructure characte rization showed that the as-prepared WO3-0.33 H2 O nanorods had a hexagonal crystal structure,and Ag and Pt nanoparticles were uniformly distributed in the WO3-0.33 H2O nano rods.Gas sensing measurements indicated that Ag and Pt nanopa rticles not only could obviously enhance NH3 sensing properties in terms of response,selectivity as well as response/recovery time,but also could reduce the optimal operating temperature at which the highest response was achieved.The highest responses of 22.4 and 47.6 for Agand Pt-doped WO3-0.33 H2O nanorods to 1000 ppm NH3 were obtained at 225 and 175℃,respectively,which were about four and eight folds higher than that of pure one at 250℃.The superior NH3 sensing properties are mainly ascribed to the catalytic activities of noble metals and the different work functions between noble metals and WO3-0.33 H2 O.展开更多
Li-rich layered oxide(LRLO)cathodes have been regarded as promising candidates for next-generation Li-ion batteries due to their exceptionally high energy density,which combines cationic and anionic redox activities.H...Li-rich layered oxide(LRLO)cathodes have been regarded as promising candidates for next-generation Li-ion batteries due to their exceptionally high energy density,which combines cationic and anionic redox activities.However,continuous voltage decay during cycling remains the primary obstacle for practical applications,which has yet to be fundamentally addressed.It is widely acknowledged that voltage decay originates from the irreversible migration of transition metal ions,which usually further exacerbates structural evolution and aggravates the irreversible oxygen redox reactions.Recently,constructing O2-type structure has been considered one of the most promising approaches for inhibiting voltage decay.In this review,the relationship between voltage decay and structural evolution is systematically elucidated.Strategies to suppress voltage decay are systematically summarized.Additionally,the design of O2-type structure and the corresponding mechanism of suppressing voltage decay are comprehensively discussed.Unfortunately,the reported O2-type LRLO cathodes still exhibit partially disordered structure with extended cycles.Herein,the factors that may cause the irreversible transition metal migrations in O2-type LRLO materials are also explored,while the perspectives and challenges for designing high-performance O2-type LRLO cathodes without voltage decay are proposed.展开更多
Aqueous Zinc-ion batteries(ZIBs),using zinc negative electrode and aqueous electrolyte,have attracted great attention in energy storage field due to the reliable safety and low-cost.A composite material comprised of V...Aqueous Zinc-ion batteries(ZIBs),using zinc negative electrode and aqueous electrolyte,have attracted great attention in energy storage field due to the reliable safety and low-cost.A composite material comprised of VO2·0.2H2O nanocuboids anchored on graphene sheets(VOG)is synthesized through a facile and efficient microwave-assisted solvothermal strategy and is used as aqueous ZIBs cathode material.Owing to the synergistic effects between the high conductivity of graphene sheets and the desirable structural features of VO2·0.2H2O nanocuboids,the VOG electrode has excellent electronic and ionic transport ability,resulting in superior Zn ions storage performance.The Zn/VOG system delivers ultrahigh specific capacity of 423 mAh·g^−1 at 0.25 A·g^−1 and exhibits good cycling stability of up to 1,000 cycles at 8 A·g^−1 with 87%capacity retention.Systematical structural and elemental characterizations confirm that the interlayer space of VO2·0.2H2O nanocuboids can adapt to the reversible Zn ions insertion/extraction.The as-prepared VOG composite is a promising cathode material with remarkable electrochemical performance for low-cost and safe aqueous rechargeable ZIBs.展开更多
The adsorption and decomposition of H2O on GaN（0001） surface have been explored employing density functional theory （DFT）. Two distinct adsorption features of H2O on GaN（0001） corresponding to molecular adsorpti...The adsorption and decomposition of H2O on GaN（0001） surface have been explored employing density functional theory （DFT）. Two distinct adsorption features of H2O on GaN（0001） corresponding to molecular adsorption and H-OH dissociative adsorption are revealed by our calculations. The activities of the surface reactions of H2O on GaN（0001） surface are investigated. For the stepwise processes of H2O decomposition into H2 in gas phase and adsorbed O atom （H2O（g）→H2O（chem）→OH（chem） ＋ H（chem）→2H（chem） ＋ O（chem）→H2（g） ＋ O（chem））, the first and second steps are facile and can even occur at room temperature; while the last two have high barriers and thus are difficult to proceed, especially the fourth step is endothermic. In short, H2O adsorption and decomposition into H2 in gas phase and adsorbed O atom on GaN（0001） surface are exothermic by -43.98 kcal/mol.展开更多
V_(3)O_(7)·H_(2)O(VO)is a high capacity cathode material in the field of aqueous zinc ion batteries(AZIBs),but it is limited by slow ion migration and low electrical conductivity.In this paper,polypyridine(PPyd)i...V_(3)O_(7)·H_(2)O(VO)is a high capacity cathode material in the field of aqueous zinc ion batteries(AZIBs),but it is limited by slow ion migration and low electrical conductivity.In this paper,polypyridine(PPyd)intercalated VO with nanoribbon structure was prepared by a simple in-situ pre-intercalation,which is noted VO-PPyd.The total density of states(TDOS)shows that after the pre-intercalation of PPyd,an intermediate energy level appears between the valence band and conduction band,which provides a step that can effectively reduce the band gap and enhance the electron conductivity.Furthermore,the density functional theory(DFT)results found that Zn^(2+)is more easily de-intercalated from the V-O skeleton,which proves that the embeddedness of PPyd improves the diffusion kinetics of Zn^(2+).Electrochemical studies have shown that VO-PPyd cathode materials exhibit excellent rate performance(high specific capacity of 465 and 192 mA h g^(-1)at 0.2 and 10 A g^(-1),respectively)and long-term cycling performance(92.7%capacity retention rate after 5300 cycles),due to their advantages in structure and composition.More importantly,the energy density of VO-PPyd//Zn at 581 and 5806 W kg^(-1)is 375 and 247 W h kg^(-1),respectively.VO-PPyd exhibits excellent electrochemical properties compared to previously reported vanadium based cathodes,which makes it highly competitive in the field of high-performance cathode materials of AZIBs.展开更多
A novel model was developed to theoretically evaluate the 02 adsorption on H-terminated Si（001）-（2×2×1） surface. The periodic boundary condition, the ultrasoft pseudopotentials technique based on density...A novel model was developed to theoretically evaluate the 02 adsorption on H-terminated Si（001）-（2×2×1） surface. The periodic boundary condition, the ultrasoft pseudopotentials technique based on density functional theory （DFT） with generalized gradient approxi,natior, （GGA） functional were applied in our ab initio calculations. By analyzing bonding energy oil site, the favourable adsorption site was determined. The calculations also predicted that the adsorption products should be Si=O and H2O. This theoretical study snpported the reaction mechanism provided by Kovalev et al, The results were also a base for further investigation of some more complex systems such as the oxida.tion on porous silicon surface.展开更多
The development of catalytic carbonylation reactions has increased considerably.Although many reviews/chapters/books on carbonylation reactions have been published,summaries on cheap metal-catalyzed catalytic carbonyl...The development of catalytic carbonylation reactions has increased considerably.Although many reviews/chapters/books on carbonylation reactions have been published,summaries on cheap metal-catalyzed catalytic carbonylation reactions of aryl halides and other chemical bonds with high dissociation energy C–Y(Y¼O,N,H)are still very rare.Focusing on green and sustainable chemistry,this review summarizes and discusses the achievements on carbonylative transformations of aryl halides(C(sp2)–X)and strong bonds C–Y(Y¼O,N,H)based on non-expensive metal catalysts(Co,Mn,Mo,Ni,Fe,Cu),photochemical and electrochemical systems developed in recent decades.展开更多
Cis-dioxo-tungsten(Ⅵ ) complex, (NH2CH2CH2NH2)[(NH2CH2CH2NH3)2WⅥO2(NHC6H4NH)2]2·H2O is synthesized at room temperature by the reaction of sodium tungstate with o-phenylenediamine. The crystal structure of compl...Cis-dioxo-tungsten(Ⅵ ) complex, (NH2CH2CH2NH2)[(NH2CH2CH2NH3)2WⅥO2(NHC6H4NH)2]2·H2O is synthesized at room temperature by the reaction of sodium tungstate with o-phenylenediamine. The crystal structure of complex was determined by X-ray diffraction structural analysis. The results show that complex belongs to monoclinic system with space group P21 / c, a=0.712 8(2) nm, b=3.081 1(10) nm, c=0.981 9(3) nm, β=102.615(4)°, V=2.104 4(11) nm3, Z=2, μ=55.26 cm-1, F(000)=1 176. Compared the complex with its analogous biomimetic complexes of the cofactor of molybdoenzymes and tungstoenzymses, it is found that the variance of the coordination atoms and the metal ions center have no influence on the coordination feature, and exhibits distored octahedral coordination with cis-dioxo o-phenylenediamine. CCDC: 252834.展开更多
基金Supported by the Natural Science Foundation of Jiangxi Province (Nos. 0220006 and 2007GZH2643)
文摘The interaction between several different metal ions and H2O along with CO2 has been researched theoretically in the CO2 photocatalytic reduction with H2O system at the B3LYP level by DFT.The computational results revealed that relatively high valence metal ions loaded on TiO2 activated the H2O and CO2 consumingly,and it might be looked as some proofs for modified photocatalyst selecting.In addition,the metal ions conducted photoelectrons to prevent the re-combination of photoelectrons and holes during the reaction process.
文摘Recently, Hsieh and Horng [1] published the paper entitled as above. In section 3 results and discussion, the authors mentioned the first and the second order kinetic models without any quotations. In fact these two kinetic models have been published [2-5]. In order to distinguish a kinetics model based on the ad- sorption capacity of a solid from the one based on the concentration of a solution, Lagergren＇s first-order rate equation has been called pseudo-first-order [6-7]. The Lagergren＇s equation has been widely cited, but there are far more mistakes made in the quotation and in the reference section of papers, including the title, the author＇s name, journal title, year of publishing, volume, and page number [3]. In addition, the second order kinetic expression for the adsorption systems of divalent metal ions using sphagnum moss peat has been reported by Ho [8].
基金Nature Science Foundation of Qinghai Province(2018-ZJ-945Q)NSFC(21573268)+1 种基金Joint Foundation of Salt Lake Chemical(U1607106)Instrument function development and technology innovation project of Chinese academy of sciences(2018g108)
文摘The microhydration structure of nickel sulfate aqueous solution has been determined via density functional theory (DFT) calculation and extended X-ray absorption fine structure (EXAFS) spectroscopy.The geometric optimization and energy calculation of nickel sulfate hydrated clusters of the molecular formula [NiSO4(H2O)n ]^0 (n=1-12) were determined via DFT using the B3LYP method.Several possible initial structures were considered for clusters of each size to locate the equilibrium geometry.Based on the DFT calculation,the favorable structure of Ni^2+ includes the six-coordinated form of [NiSO4(H2O)n ]^0 clusters.The results of hydration energy calculation suggest that the six-coordinated contact ion pair (CIP) is the stable configuration for small hydration clusters (n≤5),while the solvent-shared ion pair (SSIP) represents the favorable structure for medium hydration clusters (6≤n≤10).The solvent is separated by x water molecules (xSIP,x≥2 is the number of water molecule between Ni^2+ and SO4^2-) in larger hydration clusters (n≥11).The EXAFS analysis of the NiSO 4 aqueous solutions and NiSO4 ·6H2O solid established that Ni^2+ was surrounded by six water molecules tightly forming an octahedral structure in the first hydration shell,and no CIP was found from 0.70 mol/L to 2.22 mol/L (near saturation).The Ni-O distance and coordinated number were 2.040±0.020 and 6.0±1.0,respectively.These results are consistent with the DFT calculations for [NiSO4(H2O)n ]^0 clusters.DFT and EXAFS are powerful techniques that can be used to enhance the resolution of NiSO 4 solution microstructure.
基金supported in part by the High Performance Computing Center of Central South Universityfinancially supported by the National Natural Science Foundation of China (No.51674291)。
文摘The utilization of Ca ion as assistant depressant of CMC on talc has been widely reported.Thus,the study on the adsorption mechanism of Ca ion on talc surface is very crucial for understanding the performance of CMC on talc depression.In this paper,mechanism insights into hydrated Ca ion adsorption on talc(001) basal surface were creatively provided using DFT calculation.[Ca(H_(2)O)_6]^(2+) and [Ca(OH)(H_(2)O)_(3)]^(+) were determined as the effective hydrate components for Ca ion adsorption,and the top O site was the most favorable position for their adsorptions on talc surface.Furthermore,the adsorption mechanisms of [Ca(H_(2)O)_6]^(2+) and [Ca(OH)(H_(2)O)_(3)]^(+) on talc surface were found to be not the Ca-O chemical bond,but the hydrogen bonding formed by the H atom of the H_(2)O ligand and the surface O atom.H_(2)O acted like a bridge to connect them to the talc surface.Moreover,the hydrogen bonding was formed due to the hybridization of H 1s orbital with the O 2s,O 2p orbitals.Simultaneously,electrons transferred between the H atom and the surface O atom.This work provides theoretical insights into the Ca ion adsorption on talc surface,which can help deeply understand the talc flotation using CMC as depression.
基金supported by the Natural Science Foundation of Tianjin(No.18JCYBJC17700)the National Natural Science Foundation of China(Nos.21406164,21466035 and 22066022)the National Key Basic Research and Development Program of China(973 Program,No.2014CB239300)。
文摘The rational design of strong affinity adsorbents for heavy metal ions removal remains a critical challenge for water treatment.In this study,amorphous molybdenum sulfide composites(EDTA-MoSx(x=2,3))were fabricated via a facile hydrothermal method mediated by EDTA,which was applied to heavy metal ions(Cu^(2+),Cd^(2+),Pb^(2+),Zn^(2+)and Ni^(2+))removal from aqueous solutions.A case study for Cu^(2+)ions showed that the adsorption capacity of EDTA-MoSx(x=2,3)was superior to crystalline phase MoS2 at pH 6.0 with an initial concentration of 200 mg/L.Adsorption mechanisms of different sulfide groups and—COOH of EDTA-MoSx(x=2,3)were verified systematically via a series of experiments,characterizations,and density functional theory(DFT)calculations.Both bridging S_(2)^(2-)and—COOH covalently bonded with Cu^(2+)ions were ascribed to the critical factors for this enhanced removal efficiency on the surface of EDTA-MoSx(x=2,3).This work offers a new method to enhance the adsorption performance of molybdenum sulfide-based materials by controlling crystallinity mediated with an organic complex small molecule.
基金supported by the National Natural Science Foundation of China(Nos.51674067,51422402)FundamentalResearch Funds for the Central Universities(Nos.N180102032,N180106002,N180408018,N170106005)+3 种基金Liaoning Revitalization Talents Program(No.XLYC1807160)Liaoning BaiQianWan Talents Program(No.201892127)Open Foundation of State Key Laborato ry of Mineral Processing(No.BGRIMM-KJSKL-2019-12)Open Foundation of State Environmental Protection Key Laboratory of Mineral Metallurgical Resources Utilization and Pollution Control(No.HB201902)。
文摘Ag-and Pt-doped WO3-0.33 H2O nanorods with high response and selectivity to NH3 were synthesized from a tungsten-containing mine ral of scheelite concentrate by a simple combined process,namely by a high pressure leaching method to obtain tungstate ions-containing leaching solution and followed by a hydrothermal method to prepare corresponding nanorods.The microstructure and NH3 sensing perfo rmance of the final products were investigated systematically.The microstructure characte rization showed that the as-prepared WO3-0.33 H2 O nanorods had a hexagonal crystal structure,and Ag and Pt nanoparticles were uniformly distributed in the WO3-0.33 H2O nano rods.Gas sensing measurements indicated that Ag and Pt nanopa rticles not only could obviously enhance NH3 sensing properties in terms of response,selectivity as well as response/recovery time,but also could reduce the optimal operating temperature at which the highest response was achieved.The highest responses of 22.4 and 47.6 for Agand Pt-doped WO3-0.33 H2O nanorods to 1000 ppm NH3 were obtained at 225 and 175℃,respectively,which were about four and eight folds higher than that of pure one at 250℃.The superior NH3 sensing properties are mainly ascribed to the catalytic activities of noble metals and the different work functions between noble metals and WO3-0.33 H2 O.
基金funded by the National Natural Science Foundation of China(Grant Nos.22279092 and 5202780089).
文摘Li-rich layered oxide(LRLO)cathodes have been regarded as promising candidates for next-generation Li-ion batteries due to their exceptionally high energy density,which combines cationic and anionic redox activities.However,continuous voltage decay during cycling remains the primary obstacle for practical applications,which has yet to be fundamentally addressed.It is widely acknowledged that voltage decay originates from the irreversible migration of transition metal ions,which usually further exacerbates structural evolution and aggravates the irreversible oxygen redox reactions.Recently,constructing O2-type structure has been considered one of the most promising approaches for inhibiting voltage decay.In this review,the relationship between voltage decay and structural evolution is systematically elucidated.Strategies to suppress voltage decay are systematically summarized.Additionally,the design of O2-type structure and the corresponding mechanism of suppressing voltage decay are comprehensively discussed.Unfortunately,the reported O2-type LRLO cathodes still exhibit partially disordered structure with extended cycles.Herein,the factors that may cause the irreversible transition metal migrations in O2-type LRLO materials are also explored,while the perspectives and challenges for designing high-performance O2-type LRLO cathodes without voltage decay are proposed.
基金The authors are thankful to funds from the China Postdoctoral Science Foundation(No.RZ1900011127)Qingdao Innovation Leading Talent Program and Taishan Scholars Program and Natural Science Foundation of Shandong(No.ZR2017BEM028)+4 种基金M.S.is thankful to funds from the Science Foundation of Jiangsu Province(No.BK20171169)C.W.L.thanks the support from National Natural Science Foundation of China(No.51802168)China Postdoctoral Science Foundation(No.2018M630753)Natural Science Foundation of Shandong Province(No.ZR2018BEM006)Qingdao Postdoctoral Application Research Project.
文摘Aqueous Zinc-ion batteries(ZIBs),using zinc negative electrode and aqueous electrolyte,have attracted great attention in energy storage field due to the reliable safety and low-cost.A composite material comprised of VO2·0.2H2O nanocuboids anchored on graphene sheets(VOG)is synthesized through a facile and efficient microwave-assisted solvothermal strategy and is used as aqueous ZIBs cathode material.Owing to the synergistic effects between the high conductivity of graphene sheets and the desirable structural features of VO2·0.2H2O nanocuboids,the VOG electrode has excellent electronic and ionic transport ability,resulting in superior Zn ions storage performance.The Zn/VOG system delivers ultrahigh specific capacity of 423 mAh·g^−1 at 0.25 A·g^−1 and exhibits good cycling stability of up to 1,000 cycles at 8 A·g^−1 with 87%capacity retention.Systematical structural and elemental characterizations confirm that the interlayer space of VO2·0.2H2O nanocuboids can adapt to the reversible Zn ions insertion/extraction.The as-prepared VOG composite is a promising cathode material with remarkable electrochemical performance for low-cost and safe aqueous rechargeable ZIBs.
基金Supported by the National Natural Science Foundation of China (No. 20673019)
文摘The adsorption and decomposition of H2O on GaN（0001） surface have been explored employing density functional theory （DFT）. Two distinct adsorption features of H2O on GaN（0001） corresponding to molecular adsorption and H-OH dissociative adsorption are revealed by our calculations. The activities of the surface reactions of H2O on GaN（0001） surface are investigated. For the stepwise processes of H2O decomposition into H2 in gas phase and adsorbed O atom （H2O（g）→H2O（chem）→OH（chem） ＋ H（chem）→2H（chem） ＋ O（chem）→H2（g） ＋ O（chem））, the first and second steps are facile and can even occur at room temperature; while the last two have high barriers and thus are difficult to proceed, especially the fourth step is endothermic. In short, H2O adsorption and decomposition into H2 in gas phase and adsorbed O atom on GaN（0001） surface are exothermic by -43.98 kcal/mol.
基金supported by the National Natural Science Foundation of China (21676036)the Natural Science Foundation of Chongqing (CSTB2023NSCQ-MSX0580)the Graduate Research and Innovation Foundation of Chongqing (CYB22043 and CYS22073)。
文摘V_(3)O_(7)·H_(2)O(VO)is a high capacity cathode material in the field of aqueous zinc ion batteries(AZIBs),but it is limited by slow ion migration and low electrical conductivity.In this paper,polypyridine(PPyd)intercalated VO with nanoribbon structure was prepared by a simple in-situ pre-intercalation,which is noted VO-PPyd.The total density of states(TDOS)shows that after the pre-intercalation of PPyd,an intermediate energy level appears between the valence band and conduction band,which provides a step that can effectively reduce the band gap and enhance the electron conductivity.Furthermore,the density functional theory(DFT)results found that Zn^(2+)is more easily de-intercalated from the V-O skeleton,which proves that the embeddedness of PPyd improves the diffusion kinetics of Zn^(2+).Electrochemical studies have shown that VO-PPyd cathode materials exhibit excellent rate performance(high specific capacity of 465 and 192 mA h g^(-1)at 0.2 and 10 A g^(-1),respectively)and long-term cycling performance(92.7%capacity retention rate after 5300 cycles),due to their advantages in structure and composition.More importantly,the energy density of VO-PPyd//Zn at 581 and 5806 W kg^(-1)is 375 and 247 W h kg^(-1),respectively.VO-PPyd exhibits excellent electrochemical properties compared to previously reported vanadium based cathodes,which makes it highly competitive in the field of high-performance cathode materials of AZIBs.
文摘A novel model was developed to theoretically evaluate the 02 adsorption on H-terminated Si（001）-（2×2×1） surface. The periodic boundary condition, the ultrasoft pseudopotentials technique based on density functional theory （DFT） with generalized gradient approxi,natior, （GGA） functional were applied in our ab initio calculations. By analyzing bonding energy oil site, the favourable adsorption site was determined. The calculations also predicted that the adsorption products should be Si=O and H2O. This theoretical study snpported the reaction mechanism provided by Kovalev et al, The results were also a base for further investigation of some more complex systems such as the oxida.tion on porous silicon surface.
基金financial support from the National Key R&D Program of China(No.2023YFA1507500)We also appreciate the general support provided by Prof.Armin Borner at Leibniz-Institute for€Catalysis.
文摘The development of catalytic carbonylation reactions has increased considerably.Although many reviews/chapters/books on carbonylation reactions have been published,summaries on cheap metal-catalyzed catalytic carbonylation reactions of aryl halides and other chemical bonds with high dissociation energy C–Y(Y¼O,N,H)are still very rare.Focusing on green and sustainable chemistry,this review summarizes and discusses the achievements on carbonylative transformations of aryl halides(C(sp2)–X)and strong bonds C–Y(Y¼O,N,H)based on non-expensive metal catalysts(Co,Mn,Mo,Ni,Fe,Cu),photochemical and electrochemical systems developed in recent decades.
文摘Cis-dioxo-tungsten(Ⅵ ) complex, (NH2CH2CH2NH2)[(NH2CH2CH2NH3)2WⅥO2(NHC6H4NH)2]2·H2O is synthesized at room temperature by the reaction of sodium tungstate with o-phenylenediamine. The crystal structure of complex was determined by X-ray diffraction structural analysis. The results show that complex belongs to monoclinic system with space group P21 / c, a=0.712 8(2) nm, b=3.081 1(10) nm, c=0.981 9(3) nm, β=102.615(4)°, V=2.104 4(11) nm3, Z=2, μ=55.26 cm-1, F(000)=1 176. Compared the complex with its analogous biomimetic complexes of the cofactor of molybdoenzymes and tungstoenzymses, it is found that the variance of the coordination atoms and the metal ions center have no influence on the coordination feature, and exhibits distored octahedral coordination with cis-dioxo o-phenylenediamine. CCDC: 252834.
